Tertiary Hyperparathyroidism

OVERVIEW

Tertiary Hyperparathyroidism (THPT) is end result of long standing secondary hyperparathyroidism usually occurs in men and women with chronic kidney disease (CKD) after kidney transplant. In this case, there is an autonomous secretion of the parathyroid hormone, causing hypercalcemic state of body. The PTH hormone is secreted despite high serum calcium levels. Other rare causes of tertiary hyperparathyroidism include X-linked hypophosphatemic rickets, adult-onset (autosomal dominant) hypophosphatemic rickets, and oncogenic osteomalacia where increased phosphate levels result into decreased vitamin D and calcium levels and increased parathyroid hormone secretion. Classically in THPT; there is either hyperplasia of all parathyroid glands or adenomas are seen in single or double parathyroid glands. If untreated, this disease will affect patient survival and renal allograft. Genetically, those who have an X-linked dominant disorder that disrupts phosphate transport at the renal tubules (X-Linked hypophosphatemic rickets) and are receiving oral phosphate treatment have shown to be at high risk of developing tertiary hyperparathyroidism in the absence of secondary hyperparathyroidism. Recurring tertiary hyperparathyroidism is generally seen to be caused by incomplete parathyroidectomy without renal transplant and the risk is increased when the parathyroid tissue left after surgery is that of a nodular type.

DIAGNOSIS

Unlike PHPT, where neck ultrasound and 99mTc sestamibi scintigraphy can be done for localization, in case of SHPT and THPT bilateral neck exploration is needed except in ectopic or re-operative cases. If both preoperative imaging studies are inconclusive, then magnetic resonance imaging (MRI) and fine needle aspiration of the suspicious lesion—with measurement of parathyroid hormone in the aspirated fluid are advised.

COMPLICATIONS

Hypercalcemia and hypercalciuria both of which lead to dysfunction and loss of the renal allograft.
Acute tubular necrosis
Osteoporosis, Bone fractures (particularly in the first five years post transplantation), first six months post renal transplantation, there is a quick rate of bone loss.
Cardiovascular diseases

SIGN AND SYMPTOMS

The symptoms of THPT are similar to those of primary hyperparathyroidism (PHPT). They include

1. Reduced bone density (osteoporosis),
2. Fatigue	5. Constipation
3. Muscle weakness	6. Abdominal pain
4. Bone pain	7. Poor concentration, and/or confusion.

RISK FACTORS

Acute Pancreatitis
Malignancy of urinary tract and renal system
High levels of PTH, calcium, phosphorus and/or alkaline phosphatase at the time of transplantation.
Renal insufficiency, calcitriol deficiency, immunosuppressive medications (including steroids)
High body mass index in female gender

TREATMENT

Surgery: The main indication for treatment of tertiary hyperparathyroidism is surgery. During surgery, some or all of a defective parathyroid gland can be removed. If necessary, a surgeon can remove all four parathyroid glands if they are defective. In this instance, a small portion of healthy parathyroid tissue can be left in place to help the patient maintain a healthy PTH level.
Antibiotics: Supplementation of Vitamin D and use of cinacalcet.